Both natural and synthetic polymers, including homopolymers and copolymers, which are both biocompatible and absorbable in vivo are known for use in the manufacture of medical devices that are implanted in body tissue and absorb over time. Examples of such medical devices include suture anchor devices, sutures, staples, surgical tacks, clips, plates, screws, drug delivery devices, adhesion prevention films and foams, and tissue adhesives.
Natural polymers may include catgut, cellulose derivatives and collagen. Natural polymers typically absorb by an enzymatic degradation process in the body.
Synthetic polymers may include aliphatic polyesters, polyanhydrides and poly(orthoester)s. Synthetic absorbable polymers typically degrade by a hydrolytic mechanism. Such synthetic absorbable polymers include homopolymers, such as poly(glycolide), poly(lactide), poly(e-caprolactone), poly(trimethylene carbonate) and poly(p-dioxanone), and copolymers, such as poly(lactide-co-glycolide), poly(e-caprolactone-co-glycolide), poly(glycolide-co-trimethylene carbonate), poly(alkylene diglycolate), and polyoxaesters. The polymers may be statistically random copolymers, segmented copolymers, block copolymers or graft copolymers.
Alkyd-type polyesters prepared by the polycondensation of a polyol, polyacid and fatty acid are used in the coating industry in a variety of products, including chemical resins, enamels, varnishes and paints. These polyesters also are used in the food industry to make texturized oils and emulsions for use as fat substitutes.
Water-soluble and water-dilutable coatings that are obtained by reacting a polyglycol with an alkyd resin have been described in the paint industry.
There is a great need for polymers for use in drug delivery and medical devices, where the polymers have both low melting temperatures and low viscosities upon melting, thus permitting for solvent-free processing techniques in preparation of medical devices and compositions, can crystallize rapidly, and biodegrade within 6 months. There is also a need for polymers which are amphiphilic and self-assemble in aqueous media to form micelles that are useful for the delivery of hydrophobic drugs and for polymers that can form injectable microdispersions for delivery of hydrophilic drugs such as proteins. In addition, there is a need for polymers that would form gels in contact with water that are useful for post surgical adhesion prevention.